Programmable gain amplifiers (PGAs) are used in a variety of different electronic systems to provide an adjustable or programmable gain for amplifying an input signal. For example, PGAs can be used as an input amplifier for an analog-to-digital converter (A/D or ADC) to accommodate a wide dynamic range of input signal levels. PGAs typically employ an operational amplifier or op amp with an adjustable resistive feedback network to set the amplifier gain. The op amp receives an input signal at a first input, and provides an output signal that is related to the input signal based on the gain. The gain is determined by the impedance of the feedback path between the output and a second op amp input. Conventional PGAs employ switches to change the selection of feedback resistors to adjust the gain. However, on-chip mismatch between resistor components causes gain errors which might be unacceptable for certain applications.